β-Arrestins are known to play a crucial role in GPCR-mediated transmembrane signaling processes. However, there are still many unanswered questions, especially those concerning the presumed similarities and differences of β-arrestin isoforms. Here, we examined the roles of β-arrestin 1 and β-arrestin 2 at different levels of μ-opioid receptor (MOR)-regulated signaling, including MOR mobility, internalization of MORs, and adenylyl cyclase (AC) activity. For this purpose, naïve HEK293 cells or HEK293 cells stably expressing YFP-tagged MOR were transfected with appropriate siRNAs to block in a specific way the expression of β-arrestin 1 or β-arrestin 2. We did not find any significant differences in the ability of β-arrestin isoforms to influence the lateral mobility of MORs in the plasma membrane. Using FRAP and line-scan FCS, we observed that knockdown of both β-arrestins similarly increased MOR lateral mobility and diminished the ability of DAMGO and endomorphin-2, respectively, to enhance and slow down receptor diffusion kinetics. However, β-arrestin 1 and β-arrestin 2 diversely affected the process of agonist-induced MOR endocytosis and exhibited distinct modulatory effects on AC function. Knockdown of β-arrestin 1, in contrast to β-arrestin 2, more effectively suppressed forskolin-stimulated AC activity and prevented the ability of activated-MORs to inhibit the enzyme activity. Moreover, we have demonstrated for the first time that β-arrestin 1, and partially β-arrestin 2, may somehow interact with AC and that this interaction is strongly supported by the enzyme activation. These data provide new insights into the functioning of β-arrestin isoforms and their distinct roles in GPCR-mediated signaling.

• Klíčová slova
• Adenylyl cyclase, DAMGO, Endomorphin-2, Receptor lateral mobility, β-Arrestin, μ-Opioid receptor,
• MeSH
• adenylátcyklasy * metabolismus   MeSH
• beta arrestin 1 metabolismus   MeSH
• beta arrestin 2 metabolismus   MeSH
• beta arrestiny metabolismus   MeSH
• HEK293 buňky MeSH
• lidé MeSH
• receptory opiátové mu * metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• adenylátcyklasy * MeSH
• ARRB1 protein, human MeSH Prohlížeč
• beta arrestin 1 MeSH
• beta arrestin 2 MeSH
• beta arrestiny MeSH
• receptory opiátové mu * MeSH

Fluorescence-detected linear dichroism microscopy allows observing various molecular processes in living cells, as well as obtaining quantitative information on orientation of fluorescent molecules associated with cellular features. Such information can provide insights into protein structure, aid in development of genetically encoded probes, and allow determinations of lipid membrane properties. However, quantitating and interpreting linear dichroism in biological systems has been laborious and unreliable. Here we present a set of open source ImageJ-based software tools that allow fast and easy linear dichroism visualization and quantitation, as well as extraction of quantitative information on molecular orientations, even in living systems. The tools were tested on model synthetic lipid vesicles and applied to a variety of biological systems, including observations of conformational changes during G-protein signaling in living cells, using fluorescent proteins. Our results show that our tools and model systems are applicable to a wide range of molecules and polarization-resolved microscopy techniques, and represent a significant step towards making polarization microscopy a mainstream tool of biological imaging.

• MeSH
• analýza jednotlivých buněk * MeSH
• fluorescenční barviva metabolismus   MeSH
• fluorescenční mikroskopie * MeSH
• HEK293 buňky MeSH
• lidé MeSH
• luminescentní proteiny genetika   metabolismus   MeSH
• navrhování softwaru * MeSH
• počítačové zpracování obrazu * MeSH
• polarizační mikroskopie * MeSH
• proteiny vázající GTP genetika   metabolismus   MeSH
• rekombinantní fúzní proteiny metabolismus   MeSH
• signální transdukce MeSH
• simulace molekulární dynamiky MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• audiovizuální média MeSH
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fluorescenční barviva MeSH
• luminescentní proteiny MeSH
• proteiny vázající GTP MeSH
• rekombinantní fúzní proteiny MeSH

The interactions between TRPV1 and µ-opioid receptors (MOR) have recently attracted much attention because these two receptors play important roles in pain pathways and can apparently modulate each other's functioning. However, the knowledge about signaling interactions and crosstalk between these two receptors is still limited. In this study, we investigated the mutual interactions between MOR and TRPV1 shortly after their activation in HEK293 cells expressing these two receptors. After activation of one receptor we observed significant changes in the other receptor's lateral mobility and vice versa. However, the changes in receptor movement within the plasma membrane were not connected with activation of the other receptor. We also observed that plasma membrane β-arrestin 2 levels were altered after treatment with agonists of both these receptors. Knockdown of β-arrestin 2 blocked all changes in the lateral mobility of both receptors. Furthermore, we found that β-arrestin 2 can play an important role in modulating the effectiveness of ERK1/2 phosphorylation after activation of MOR in the presence of TRPV1. These data suggest that β-arrestin 2 and ERK1/2 are important mediators between these two receptors and their signaling pathways. Collectively, MOR and TRPV1 can mutually affect each other's behavior and β-arrestin 2 apparently plays a key role in the bidirectional crosstalk between these two receptors in the plasma membrane.

• Klíčová slova
• ERK1/2, TRPV1, biased signaling, receptor lateral mobility, β-arrestin 2, μ-opioid receptor,
• MeSH
• arrestiny metabolismus   MeSH
• beta arrestin 2 metabolismus   fyziologie   MeSH
• beta arrestiny metabolismus   MeSH
• buněčná membrána metabolismus   fyziologie   MeSH
• fosforylace MeSH
• HEK293 buňky MeSH
• kationtové kanály TRPV metabolismus   fyziologie   MeSH
• lidé MeSH
• MAP kinasový signální systém fyziologie   MeSH
• morfin metabolismus   MeSH
• opioidní analgetika metabolismus   MeSH
• receptory opiátové mu metabolismus   fyziologie   MeSH
• receptory opiátové metabolismus   MeSH
• signální transdukce MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• arrestiny MeSH
• beta arrestin 2 MeSH
• beta arrestiny MeSH
• kationtové kanály TRPV MeSH
• morfin MeSH
• opioidní analgetika MeSH
• receptory opiátové mu MeSH
• receptory opiátové MeSH
• TRPV1 protein, human MeSH Prohlížeč

The receptor channel transient receptor potential vanilloid 1 (TRPV1) functions as a sensor of noxious heat and various chemicals. There is increasing evidence for a crosstalk between TRPV1 and opioid receptors. Here we investigated the effect of the prototypical TRPV1 agonist capsaicin and selected opioid ligands on TRPV1 movement in the plasma membrane and intracellular calcium levels in HEK293 cells expressing TRPV1 tagged with cyan fluorescent protein (CFP). We observed that lateral mobility of TRPV1 increased after treatment of cells with capsaicin or naloxone (a nonselective opioid receptor antagonist) but not with DAMGO (a μ-opioid receptor agonist). Interestingly, both capsaicin and naloxone, unlike DAMGO, elicited intracellular calcium responses. The increased TRPV1 movement and calcium influx induced by capsaicin and naloxone were blocked by the TRPV1 antagonist capsazepine. The ability of naloxone to directly interact with TRPV1 was further corroborated by [3H]-naloxone binding. In conclusion, our data suggest that besides acting as an opioid receptor antagonist, naloxone may function as a potential TRPV1 agonist.

• Klíčová slova
• calcium, fluorescence recovery after photobleaching, naloxone, receptor lateral mobility, transient receptor potential vanilloid 1,
• MeSH
• buněčná membrána metabolismus   MeSH
• HEK293 buňky MeSH
• kapsaicin analogy a deriváty   farmakologie   MeSH
• kationtové kanály TRPV agonisté   genetika   metabolismus   MeSH
• lidé MeSH
• ligandy MeSH
• naloxon farmakologie   MeSH
• narkotika - antagonisté farmakologie   MeSH
• vápník metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• kapsaicin MeSH
• kationtové kanály TRPV MeSH
• ligandy MeSH
• naloxon MeSH
• narkotika - antagonisté MeSH
• TRPV1 protein, human MeSH Prohlížeč
• vápník MeSH